Published at 10:01 PM EDT on May 21, 2018 | Updated at 6:20 AM EDT on May 22, 2018

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A "LOVE" sculpture by artist Robert Indiana (inset) in John F. Kennedy Plaza, commonly known as Love Park, in Philadelphia, May 21, 2018.

Pop artist Robert Indiana, best known for his 1960s LOVE series, has died at his island home off the coast of Maine. He was 89.

Indiana died on Saturday from respiratory failure at his Victorian home in a converted Odd Fellows hall, a fraternal order lodge, where he had lived for years on Vinalhaven Island, said James Brannan, his attorney.

Friends had expressed concern for his well-being because the reclusive artist had not been heard from for some time. A lawsuit filed in New York City the day before his death suggested he was purposefully isolated by his caretakers.

The artist's "LOVE" sculpture, in which the "L'' and a leaning "O'' sit atop the "V'' and the "E," is instantly recognizable worldwide. But he has created other works as well, including a HOPE design, similar to LOVE, in honor of former President Barack Obama.

In his later years, he was known for living an increasingly reclusive life 15 miles (24 kilometers) off the mainland on Vinalhaven, where he moved in 1978.

Kathleen Rogers, a friend and former publicist, told The Associated Press that she was so concerned she contacted the Maine Department of Health and Human Services to investigate six to eight weeks ago.

Through tears, she said did not want Indiana to be remembered for shutting out friends and closing his studio.

"He was a better guy than he's been portrayed as being. He was reclusive, cantankerous and sometimes difficult. But he was a very loyal, loving man. He was the architect of love," she said.

As the story goes, Indiana, an Indiana native, settled in Maine after getting fed up with the art scene in New York.

But he told The Associated Press in 2009 that he moved to his house — which a benefactor bought for him — when he needed a place to go after his lease ran out on his five-story studio and gallery in the Bowery section of New York City.

His desire for solitude was legendary.

He once stood up President Barack Obama at the White House. Another time he made a crew from NBC's "Today" show wait three days on the island before he would let them interview him. In 2014, he disappointed dozens of fans by failing to make an appearance outside his home for an event dubbed International HOPE Day, which was inspired by his creativity. Events were held in several locations around the world.